Peak Inverse Voltage (PIV)
Definition:
The diode should not conduct when its anode has more negative potential with respect to the cathode. The maximum value of the reverse voltage that a PN junction or diode can withstand without damage is known as diode Peak Inverse Voltage(PIV) or Peak Reverse Voltage(PRV). The different diodes has different peak inverse voltages and its value can be find in the manufacturer's data sheet.
Suppose diode PIV is 50 volts, if the voltage under reverse bias condition increase above 50 volts the diode will permanently damage.
PN junction or diode is widely used for converting AC into DC. The main component of the rectifier is diode. The diode goes under the reverse bias for every half cycle of the AC waveform. During negative half cycle the diode does not conduct and behaves as open circuit as long as the reverse voltage is equal to PIV of the diode. The total negative voltage appears across the diode, and it should sustain this reverse voltage across the junction. Therefore, at the time of rectifier design the PIV of the diode is one of the important parameter.
The selection of the peak inverse voltage of the diode depends on the type of rectifier circuit. PIV of full wave controlled rectifier is Vm, and PIV of centre tap full wave rectifier is 2Vm. The diode must be selected accordingly.
Example:
What should be the PIV of the diode for 12 VAC to 12 DC rectifier circuit?
1. For full wave bridge rectifier
2. For Center tap full wave rectifier
RMS value of the AC = 12 Volts
Peak value of AC Vm = √2 Vrms
Peak value of AC Vm = 1.414 x 12 = 16.96 Volts
PIV for full wave bridge rectifier > 16.96 V
PIV for center tap full wave rectifier > 2 x 16.96= 33.92 V
Therefore, the PIV of the diode should be 20 volts and 40 volts for full wave rectifier and center tap full wave rectifier respectively.
